In 1965, the Ford Motor Company developed the twin I-beam (TIB) front suspension system for their two wheel drive F series trucks. Later in 1980, Ford incorporated a differential into the driver side beam of the TIB. Labeled the twin traction-beam (TTB) front suspension system, Ford installed this powered version of the TIB in their four wheel drive F-series trucks. Over time, both the TIB and TTB earned the reputation as the first mass-produced long travel independent front suspension systems for a vehicle. Simple yet rugged in design, the TIB and TTB front suspension systems are based on a configuration that utilizes a single beam and trailing control arm per frame side such that—beginning with, say, the front driver wheel—one end of the beam is attached to a cross-member next to the passenger side of the frame, then the beam is directed laterally towards the driver side of the frame such that the other end of the beam is attached to the driver steering knuckle. The design is completed by repeating this process beginning with the front passenger wheel. The trailing control arms act like radius arms and stabilize the beams against uncontrolled front-to-back motion. By stretching across from one frame side to the other, the beams endow the TIB and TTB with an enviable long travel capability, and by operating in conjunction with the control arms also act to invoke a change in both caster and camber angles during suspension movement.
Given that many types of production-based vehicles are routinely used in industries that involve off-road driving, e.g., construction, farming and ranching, mining, forestry, gas and oil exploration, that many obstacles—e.g., boulders, fallen trees, ravines, cliffs—encountered off-road exceed the limits of suspension travel, and that handling quality is reduced by changes in caster and camber angles during suspension travel, then automobile manufacturers and numerous other industries would greatly benefit from an independent suspension system that possessed the long travel capability characteristic of the TIB and TTB front suspension systems that also retained caster and camber angles throughout suspension travel.
In principle, the TIB and TTB suspension systems can be re-designed to maintain both caster and camber angles by adding an additional beam and trailing control arm to the existing configuration of a single beam and trailing control arm per frame side. With the addition of another beam and trailing control arm, this re-design represents a configuration of four links per frame side, or more specifically, four links per wheel. In effect, this re-design refers to a variation of the modern double wishbone (aka, double A-arm) suspension system used by automobile manufacturers since the 1960s. The present invention presents this variation of the modern double wishbone suspension system as a design concept that possesses the long travel capability characteristic of the TIB and TTB front suspension systems that also retains caster and camber angles throughout suspension travel.
The present invention represents a system of four control linkages per wheel. The system of four control linkages represents a type of independent suspension system analogous to a a double A-arm (or wishbone) suspension system, and acts to preserve both camber and caster angles as well as uncontrolled side-to-side and front-to-back motions through the full range of travel.